Advances In Ellipsoidal Cavity Expansion With Tresca Material

Analysis of the expansion of cylindrical and spherical cavities in soil and rock provides a surprisingly versatile and accurate geomechanics approach for study of important problems in geotechnical engineering. It is necessary to extend the cavity expansion methods. The primary objective of this study is to perform ellipsoidal cavity expansion analysis in geotechnical engineering area for implementing and improving the cavity expansion methods.Adopted theoretical analysis, numerical simulation and physical simulation test, Oval cavity(which shape is different from circle and cylinder ) expansion problem is studied.Through complex variable methods of conformal transformation, elastic properties and displacement of ellipsoidal cavity in infinite homogeneity soil are studied. And the plastic properties which includs elastio-plastic boundary's figure, influecing factor and solving methods also have been reasearched by supposing for Tresca matria. At the same time the slip line field around the ellipse are given by using difference methods.By analogying the hollow sphere expansion and thick-walled cylider expansion, through changing the figure factor k value in equilibrium equation, the stress and displacement formula both in elastic state and in plastic state are given for the ellipsoidal expansion. And using the model test parameter, the theoretical result of test's stress and displacement are sloved.The paper has also studied the similar cylindrical expansion from the perspective of indoor physical model test. By changing the test materials, it is the first innovation to performance the measurable materials in studying the cavity expansion problems. And it has acheieved the resistance ratio around the cavity, by compare to the resistance ratio versus strain in material testing, the strain field around similar-cylindrical cavity has gain. The resistance ratio versus strain is different in the elastic state and in the plastic state, so it can deduce the material's elastic or plastic state under different uniform internal pressure at the cell.Though numerci analysis, it has been found that, at low internal pressure the cell has a relative large deformed, and at higher internal pressure level the cell's plastic deformed has a feature of tenting for circle figure. This is consistent with theoretical analysis.